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Is that for over or under bias?

At my current settings of +/- .500mv, the amp runs quite cool, perhaps that would change with an increase in power demand. Is the distortion you are referring to crossover/notch distortion?

Put it all back together and hooked up the (fused) JBL`s and all seems well. Cant really drive it hard at this late hour but I sure will tomorrow. I`ll just keep it running at a low level in the mean time. Simply ecstatic the amp is working again. I`m curious as to what the consequences of...

I carefully loaded the outputs following Joe`s suggestion today, one horizontal row at a time testing for collector to chassis shorts and bring it up on the DBT/Variac combo at every step. For the first time in nearly 3 months, she sings, I cant believe it. Bias is still above spec at .525 on...

:) http://www.youtube.com/watch?v=xos2MnVxe-c

One step forward, two steps back Replaced TO3 mica`s. Q11 collector to chassis 600K Q12 collector to chassis 5K and increases Those figures the same for L and R, before and after mica change. Replaced out of spec Right channel out of spec R38, 39, picked up a .116 bias were there...

I`ll tend to those asap, As for a funky insulator, the problem would have followed the Left to Right driver swap, no?

Pins 3 and 4 lifted, reconnecting pin 4 brings offset values down to normal. 10k is still across outputs R38,39 test: Left R38=10.7R R39=10.9R Right R38=13.6R R39=20.8R These are in circuit values Please refer to my earlier mica post

That's not a good thing, is it? :)

Both channel offset numbers are positive

D 14 ,15 are new on both channels, they measure identically. Lifting pin 4 gets the bias up to .192 but +11vdc offset, that gradually decreases. There is no protection circuitry.

Yes

No change

Left Bias .126 Offset.013 Right Bias .000 Offset .06

I`m all ears. Just out of curiosity, do the high voltages have anything to do with the fact no output transistors are connected?

This thing refuses to bias. 2N5088s shifted voltages up another 150-200mv in the wrong direction, offsets remain the same :confused2:

Got ya.

Huh?

Is bias set at every horizontal step or just the once at the (pre)driver stage?

So it`s just a matter of loading a horizontal row, bulb testing, offset testing and moving on up?